If you go back in time, 23andMe was founded to collect genetic data with the goal of using that data to improve the health condition of humanity.
Over time it became clear that 23andMe's data set had limited predictive ability for health for a number of technical reasons (previously, dahinds, one of their statistical geneticists, has defended the quality of their predictions on HN, you can search for his comments. I suspect he can no longer comment on HN because of 23&Me's security debacle).
However, around that same time, 23&Me's dataset turned out to be excellent for ancestry analysis. It's generally considered fairly accurate (not just 23&Me- the entire process of ancestry through snp genotyping workings really well).
I never did 23&Me but my dad did- and he learned he has children all around the US (half brothers and sisters of mine) from some samples he provided some 45+ years ago. Both my dad and those people gained value from making that connection. It's interesting because my dad had already done most of the paper research (including going to SLC to visit the Mormon archives) to identify our obvious ancestors, and these relatives would never have shown up.
